CNS stimulants (Psychostimulants, Psychomotor Stimulants) Flashcards
CNS stimulants?
●CNS stimulants are drugs which cause, a temporary increase of mental
and physical activity.
The most important groups of psychostimulants include?
●The derivatives of phenylalkylamine and their analogs
(the group of amphetamine):
》amphetamine,
》methylphenidate;
●the derivatives of methylxanthine:
▪︎caffeine,
▪︎theophylline.
Amphetamine & it’s analogs.
The mechanism of the action.
●The mechanism of the action of amphetamine and its analogs is ▪︎the stimulation of the release of norepinephrine and dopamine
to the synaptic cleft leading to the ▪︎increased transmission through adrenergic and dopaminergic synapses (indirect adrenomimetic and dopaminomimetic effect).
▪︎Also amphetamine blocks the reuptake of norepinephrine and dopamine.
The effects of amphetamine?
●The stimulant effect on the CNS is expressed by,
the increased mental activity,
improved attention
short-term memory,
decreased need for sleeping,
improved mood (euphoria).
●High doses of amphetamine can cause symptoms of psychosis (hallucinations, delusions, excitement).
●Another central effect is a
decrease of appetite (due to the increase of the inhibitory influence of norepinephrine and dopamine on the center of the appetite in the hypothalamus.
●The peripheral effects of amphetamine are
vasoconstriction,
increase of the blood pressure, tachycardia,
dilation of pupils.
●The activation of transmission through the sympathetic nerves is responsible for these effects.
Most important adverse effects of amphetamine?
●the development of drug dependence (mainly psychological dependence, symptoms of the depression can be observed after rapid withdrawal of amphetamine).
●Other adverse effects include the,
▪︎symptoms of the excessive CNS stimulation (impairment of sleeping, excitement, irritability, nervousness) and
▪︎peripheral cardiovascular symptoms (tachycardia, hypertension).
●In comparison with amphetamine methylphenidate has less significant
cardiovascular effects
& low risk of drug dependence.
Application amphetamine & its analogs?
●Due to the high potential of abuse and drug dependence these drugs are rarely used now in official medicine.
●The indications for the use of them include:
▪︎narcolepsy is a chronic neurologic disease,
which is expressed by
excessive daytime sleepiness and episodes of suddenly appearing muscle
weakness;
▪︎attention deficit hyperactivity disorder (ADHD) is a mental disorder in children, which is characterized by impaired attention and increased activity.
Psychostimulant drugs are approved in the USA for the treatment of this disorder;
methylphenidate is used more widely for this purpose.
The use of psychostimulants for ADHD is not approved in all countries.
Methylxanthine derivatives. Caffeine & Theophyline. MOA?
●the inhibition of phosphodiesterase the enzyme responsible for the inactivation of CAMP
the inhibition of this enzyme leads to the increase in amount of cAMP in the cells.
●the block of adenosine receptors.
The effects of caffeine and other methylxanthines
include
mild stimulation of the CNS (the decrease of fatigue, decreased need for sleeping).
High doses of caffeine can increase the heart rate and contractility as well as blood pressure.
▪︎Also, they stimulate the secretion of hydrochloric acid in the stomach, so the patients with peptic ulcer must avoid beverages containing caffeine.
A useful effect of methylxanthines (especially theophylline) is the relaxation of bronchial smooth muscles.
Caffeine is used in apnea of premature children (the main mechanism of the action, in this case, is the stimulation of the respiratory center).
Also, sometimes it is used in hypotension.
Theophylline and its water-soluble analog aminophylline are used in bronchial asthma (see “Drugs acting on the respiratory system”).
What are the other CNS stimulants?
Atomoxetine
Modafinil & armodafinil
Atomoxetine?
●Is a norepinephrine & dopamine reuptake inhibitor approved for the treatment of ADHD
●Also blocks glutamate NMDA receptors, this effect can also contribute to the beneficial effect of the drug in ADHD.
●In comparison with amphetamine atomoxetine has a low risk of abuse and drug dependence.
Modafinil & armodafinil?
●Modafinil and armodafinil are sometimes referred as eugeroic
(wake-fulness-promoting drugs).
They are used in the treatment of narcolepsy.
Non-medical application of these drugs includes the
use of them by militaries in conditions when sleep deprivation is necessary.
The most known mechanism of the action of modafinil and armodafinil is a block of the reuptake of dopamine.
Armodafinil acts also as a partial agonist of dopamine D₂ receptors.
These drugs have very low potential for drug dependence.
The psychostimulant effect is also characteristic of cocaine, but it is not
used as a stimulant drug in official medicine due to the high risk of drug dependence.
On the other hand, it can be used as a local anesthetic (see above).
